Heretofore, when using hand held calculators such as a Hewlett-Packard HP-41C, in order to have a particular program designed for the calculator, it required a substantial period of time and costs in that the information had to be forwarded to the company which normally made ROM chips that were adapted to be plugged into sockets carried on the top portion of the calculator.
While the chip and particular programs did work satisfactorily in the hand held calculator, they did not provide the versatility normally available in EPROM chips.
One disadvantage of utilizing EPROM chips in remote boxes is that there is a substantial amount of power drain while the chip is turned on for transferring the data consisting of the program from a remote source to the calculator.
The use of external batteries is not practical due to the difficulty of constructing a circuit so that the power source for the remote apparatus and the calculator are compatible, and the circuit be designed so that if there is a power failure in the remote source, it does not destroy the programs and information stored within the calculator.
It has been known to selectively remove power from components forming part of digital computer systems when processing is completed in order to minimize power requirements. One such device is disclosed in U.S. Pat. No. 4,171,539.
Another power supply control system for memory devices is disclosed in U.S. Pat. No. 4,141,611.
In U.S. Pat. No. 4,208,724, there is disclosed a system and method for clocking data between a remote unit and a local unit. Other U.S. Pat. Nos. that were developed during a search and may be of interest are as follows:
______________________________________ 4,125,869; 4,145,741; 4,164,786; 3,726,569; 4,009,379; 4,080,659; 4,317,180; 4,151,611. ______________________________________